Hello,
In fact the “copy paste” function between 2 templates already exists at Wix:
https://support.wix.com/en/article/wix-editor-copying-and-pasting-a-page-to-another-site
But I had already approached the question in another form in the past in which I asked Wix to set up an interface for companies that manage a network for example (real estate agency etc…) in order to be able to easily update days of mini websites with easy-to-integrate content. This seems to me to be somewhat in line with your request: 1 content for several websites.
Beyond this request, for SEO it’s not very good (duplicate content) but maybe it’s purely informative.
Ps: did you make your request officially on the “Feature Request” page?
https://community.wix.com/partners/forum/partner-announcements/feature-request-post-reminder
See u
Denis